Device and method for measuring transmittance of polarized light by adopting two-position method

Abstract

The invention discloses a device and method for measuring the transmittance of polarized light by adopting a two-position method, and relates to the technical field of light transmittance measurement, and the device comprises a laser light source which is installed on a collimator and is used for transmitting linear polarization laser to the collimator; the collimator is mounted on the front side of the optical element to be measured and used for converting the linearly polarized laser into parallel light, emitting the parallel light, controlling the laser light source to synchronously rotate and emitting the parallel light at different rotation angles; the diaphragm is arranged at the exit port of the collimator and is used for adjusting the spot size of the emergent parallel light; the power measurer is used for measuring the optical power when the parallel light does not pass through the to-be-measured optical element and the optical power when the parallel light passes through the to-be-measured optical element at different angles; and the processor is used for calculating the average transmittance of the optical element to be measured according to the optical power measured by the power measurer. According to the invention, the transmittance of the polarized light can be measured simply, accurately and quickly.

Description

Technical Field

[0001] The present invention relates to the technical field of polarized light transmittance measurement, and in particular to a device and method for measuring polarized light transmittance by adopting a two-position method. Background Art

[0002] Optical components refer to physical components used to control and manipulate light, usually including windows, spherical lenses, aspherical lenses, cylindrical lenses, prisms, galvanometer mirrors, filters, etc. Optical components can change the direction, intensity, phase, polarization and other properties of light through reflection, refraction, diffraction, transmission, etc., and are therefore widely used in communication technology, laser technology, imaging technology, biomedicine, optical measurement and detection, lighting and display, military and security, scientific research and education and other fields.

[0003] Polarized light transmittance is an important performance indicator of optical elements. It characterizes the ratio of the outgoing light flux to the incident light flux of the optical element. The quality of polarized light transmittance affects the brightness, clarity and signal-to-noise ratio of the image when observing the image. At present, there are many related technologies related to the measurement of polarized light transmittance in the prior art. For example, the patent document with publication number CN102486435A discloses a test system and test method for the dynamic transmittance of a λ / 2 voltage electro-optical switch. The test system includes a laser light source, a polarizer, an analyzer, a polarization splitter, a λ / 2 wave plate, a beam expander, an oscilloscope and a data processing module. When using the test system, the λ / 2 voltage electro-optical switch is placed between the polarizer and the analyzer, and the waveform probe of the oscilloscope is placed along the outgoing light direction of the analyzer. The test system and test method can reduce the error caused by the fluctuation of the pulse energy of the laser light source, and can measure the dynamic transmittance of λ / 2 voltage electro-optical switches of various calibers. However, after careful analysis, it was found that this technology is only suitable for measuring optical components with relatively simple structures. When the optical components have complex structures and include a spectroscopic system, this technology cannot accurately measure the transmittance of the spectroscopic system. Therefore, its scope of application is narrow and its practicality is poor. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and to provide a device and method for measuring the transmittance of polarized light using a two-position method. The present invention can simply, accurately and quickly measure the transmittance of polarized light, thus solving the technical problems of the existing measurement technology having a narrow range and poor practicality.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a device for measuring polarized light transmittance using a two-position method, comprising:

[0007] A laser light source is installed on the collimator and is used to emit linearly polarized laser light to the collimator;

[0008] A collimator, installed in front of the optical element to be measured, is used to convert linearly polarized laser light into parallel light, to emit parallel light, and to control the synchronous rotation of the laser light source and to emit parallel light at different rotation angles;

[0009] The aperture is installed at the exit of the collimator to adjust the spot size of the exiting parallel light;

[0010] A power meter is used to measure the optical power of parallel light before and after passing through the optical element to be measured at different angles;

[0011] The processor is used to calculate the average transmittance of the optical element to be measured according to the optical power measured by the power meter.

[0012] The laser light source is fixed on the incident focal plane of the collimator and is close to the emission port.

[0013] The divergence angle of the parallel light emitted by the collimator is less than 1 mrad.

[0014] The power measuring device comprises a photoelectric detector and an optical power meter, and the optical power meter is connected to the photoelectric detector and the processor respectively.

[0015] The spot area of ​​the emitted light is smaller than the detection target area of ​​the power measuring device.

[0016] A scale plate for measuring the rotation angle of the collimator is installed at the emission port of the collimator.

[0017] The output power of the laser light source is at the mW level.

[0018] The collimator is an off-axis reflective collimator.

[0019] In a second aspect, the present invention provides a method for measuring polarized light transmittance using a two-position method, comprising the following steps:

[0020] Step S1: Control the laser light source and the collimator to remain fixed at the initial angle A, first place the power meter in front of the optical element to be measured, measure the optical power of the parallel light before it passes through the optical element to be measured, and record it as M; then place the power meter behind the optical element to be measured, measure the optical power of the parallel light after it passes through the optical element to be measured, and record it as m; obtain the polarized light transmittance T of the optical element to be measured at the initial angle A based on the optical power M and the optical power m A ;

[0021] Step S2: Control the laser light source and the collimator to rotate 90 degrees along the optical axis, repeat step S1, obtain the optical power M' before the collimator passes through the optical element to be measured and the optical power m' after the collimator passes through the optical element to be measured, and then obtain the polarized light transmittance T of the optical element to be measured after rotating 90 degrees according to the optical power M' and the optical power m'. A+90 ;

[0022] Step S3: The processor calculates the polarized light transmittance T in step S1. A and the polarized light transmittance T in step S2 A+90 The average transmittance T of the optical element to be tested is calculated.

[0023] In step S1, the polarized light transmittance T A The calculation formula is:

[0024]

[0025] In step S2, the polarized light transmittance T A+90 The calculation formula is:

[0026]

[0027] In step S3, the calculation formula of the average transmittance T is:

[0028]

[0029] By adopting the above technical solution, the beneficial technical effects of the present invention are:

[0030] 1. In the prior art, when using laser to measure the polarized light transmittance of an optical element, since the laser is linearly polarized light, the corresponding energy intensity is different when the laser light source rotates at different angles, resulting in the inability to accurately obtain the polarized light transmittance of the optical element. The present invention uses a measuring device and method consisting of a laser light source, a collimator, an aperture, a power meter and a processor. By fixing the laser light source at the incident focal plane of the collimator, the transmittance can be measured by rotating the collimator. This is not only simple to operate, but also suitable for measuring optical elements of different complex structures, and has greater practicality.

[0031] 2. The present invention fixes the laser light source at the incident focal plane of the collimator and close to the exit port, which has the advantage of ensuring that the light emitted by the collimator is parallel light.

[0032] 3. The present invention designs the divergence angle of the parallel light emitted by the collimator to be less than 1 mrad, thereby improving the parallelism of the emitted light and facilitating the measurement of the transmittance of an optical system with a long optical path.

[0033] 4. The present invention adopts a photoelectric detector and an optical power meter to measure optical power, which has the advantages of simple structure, convenient measurement and high accuracy.

[0034] 5. The present invention designs the spot area of ​​the emitted light to be smaller than the detection target area of ​​the power meter, which has the advantage of improving the accuracy of the measurement.

[0035] 6. The present invention facilitates measurement personnel to accurately control the rotation angle of the collimator through the graduated dial, thereby facilitating accurate acquisition of polarized light transmittance at different rotation angles.

[0036] 7. The output power of the laser light source used in the present invention is at the mW level, and the laser light source has a relatively small power, which is beneficial to ensure measurement safety.

[0037] 8. The present invention adopts an off-axis reflective collimator so that the outgoing light has no central obstruction, which is beneficial to further improve the accuracy of measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the structure of the present invention.

[0039] Marked in the figure: 1. laser light source, 2. collimator, 3. aperture, 4. power meter, 5. processor, 6. parallel light. DETAILED DESCRIPTION

[0040] Example 1

[0041] like Figure 1 As shown, this embodiment provides a device for measuring polarized light transmittance using a two-position method, which includes a laser light source 1, a collimator 2, an aperture 3, a power meter 4 and a processor 5. Among them,

[0042] The laser light source 1 is installed on the collimator 2 , and its output power is at the mW level, and is used to emit linearly polarized laser light to the collimator 2 .

[0043] Furthermore, the laser light source 1 is fixed at the incident focal plane of the collimator 2 and close to the emission port to ensure that the light emitted by the collimator 2 is parallel light 6 .

[0044] The collimator 2 is installed in front of the optical element to be measured, and is used to convert the linearly polarized laser into parallel light 6, to emit the parallel light 6, and to control the laser light source 1 to rotate synchronously and emit the parallel light 6 at different rotation angles.

[0045] Furthermore, the collimator 2 is preferably an off-axis reflective collimator, and the divergence angle of the parallel light 6 emitted by the collimator 2 is less than 1 mrad, thereby obtaining the emitted parallel light 6 without central obstruction and with better parallelism.

[0046] The aperture 3 is installed at the exit of the collimator 2 and is used to adjust the spot size of the exiting parallel light 6 , specifically to make the spot area of ​​the exiting light smaller than the detection target area of ​​the power meter 4 .

[0047] The power measuring device 4 is used to measure the optical power of the parallel light 6 before it passes through the optical element to be measured and the optical power of the parallel light 6 after it passes through the optical element to be measured at different angles.

[0048] The processor 5 is used to obtain the optical power of the parallel light 6 before and after passing through the optical element to be measured measured by the power meter 4, and calculate the average transmittance of the optical element to be measured based on the obtained optical power.

[0049] It should be noted that the number of the above-mentioned power measuring devices 4 is preferably one set. When actually measuring, the power measuring devices 4 can be placed between the collimator 2 and the optical element to be measured (in front of the optical element to be measured) and at the rear of the optical element to be measured. Of course, without considering the cost, the number of the power measuring devices 4 can also be two sets. The two sets of power measuring devices 4 can be placed between the collimator 2 and the optical element to be measured (in front of the optical element to be measured) and at the rear of the optical element to be measured. When measuring the optical power of the parallel light 6 after passing through the optical element to be measured, the power measuring device 4 between the collimator 2 and the optical element to be measured (in front of the optical element to be measured) can be removed.

[0050] According to a preferred implementation of this embodiment, the power measuring device 4 includes a photodetector and an optical power meter, the photodetector has a detection target surface for detecting the parallel light 6, and the spot area of ​​the outgoing light processed by the collimator 2 should be smaller than the detection target surface area of ​​the power measuring device 4. The optical power meter is connected to the photodetector and the processor 5 respectively, and the optical power meter obtains a specific optical power value according to the detection result of the photodetector, and sends the obtained optical power value to the processor 5 for calculation.

[0051] According to another preferred implementation of this embodiment, a dial for measuring the rotation angle of the collimator 2 is installed at the exit of the collimator 2. During measurement, the measurement personnel can accurately control the rotation angle of the collimator 2 and the laser light source 1 according to the dial.

[0052] The measuring principle of the present embodiment is: firstly, the laser light source 1 and the collimator 2 are controlled to remain fixed at the initial angle, and the optical power of the parallel light 6 before and after the optical element to be measured can be measured by the power meter 4. Then, the laser light source 1 and the collimator 2 are controlled to rotate a certain angle, such as 90 degrees, 180 degrees, 240 degrees, etc., and the optical power of the parallel light 6 before and after the optical element to be measured and after the optical element to be measured can be measured by the power meter 4 at each angle. Finally, the processor 5 can calculate the average transmittance of the optical element to be measured based on the measured optical power. The present embodiment can accurately obtain the transmittance of the optical element to be measured by at least one rotation and two measurements, and has the advantages of simple structure, convenient operation and accurate measurement.

[0053] The two-position method described in the present invention refers to obtaining the transmittance of the optical element to be measured by measuring at two positions respectively.

[0054] Example 2

[0055] This embodiment provides a method for measuring polarized light transmittance using a two-position method. The method is mainly implemented based on the device of Embodiment 1 and includes the following steps:

[0056] Step S1: Install the laser light source 1 at the incident focal plane of the collimator 2, control the laser light source 1 and the collimator 2 to remain fixed at the initial angle A, first place the power meter 4 in front of the optical element to be measured, measure the optical power of the parallel light 6 before it passes through the optical element to be measured, and record it as M; then place the power meter 4 behind the optical element to be measured, measure the optical power of the parallel light 6 after it passes through the optical element to be measured, and record it as m; finally, obtain the polarized light transmittance T of the optical element to be measured at the initial angle A according to the optical power M and the optical power m A .

[0057] Specifically, the polarized light transmittance T A The calculation formula is:

[0058]

[0059] It should be noted that, during the actual measurement in step S1, the optical power m may be measured first, and then the optical power M. In addition, the number of the power measuring devices 4 is preferably one set, and the power measuring devices 4 may be placed at corresponding positions according to actual measurement requirements.

[0060] Step S2: Control the laser light source 1 and the collimator 2 to rotate 90 degrees along the optical axis, repeat step S1, obtain the optical power M' of the parallel light 6 before passing through the optical element to be measured and the optical power m' of the parallel light 6 after passing through the optical element to be measured, and then obtain the polarized light transmittance T of the optical element to be measured after rotating 90 degrees according to the optical power M' and the optical power m'A+90 .

[0061] Specifically, the polarized light transmittance T A+90 The calculation formula is:

[0062]

[0063] Step S3: The processor 5 calculates the polarized light transmittance T in step S1. A and the polarized light transmittance T in step S2 A+90 The average transmittance T of the optical element to be measured is calculated, and the average transmittance T is the transmittance T of the optical element to be measured.

[0064] Specifically, the calculation formula of the average transmittance T is:

[0065]

[0066] It should be noted that the calculation of the average transmittance in this embodiment is not limited to the polarized light transmittance T at the initial angle A. A and the transmittance of polarized light after rotating 90 degrees T A+90 , and can also include polarized light transmittance at other different angles.

[0067] Example 3

[0068] This embodiment takes the measurement of polarized light transmittance of a beam splitter prism by a laser light source 1 with a wavelength of 635 nm as an example, and uses the device of Embodiment 1 and the method of Embodiment 2 to measure the polarized light transmittance of the beam splitter prism. The specific process is as follows:

[0069] 1) Fix the 635nm laser light source 1 and the collimator 2, and install a rotating dial at the exit of the collimator 2 to observe the spin angle of the collimator 2. For example, when the collimator 2 is at position 0 and the parallel light 6 does not pass through the beam splitter prism, the optical power meter reading is M. After the parallel light 6 passes through the beam splitter prism, the optical power meter reading is m. Measure the polarized light transmittance of the beam splitter prism. At this time, the polarized light transmittance is T0 = 1.73%.

[0070] 2) Keep the laser light source 1 and the collimator 2 fixed, rotate the collimator 290 degrees along the optical axis, at position 90, when the parallel light 6 does not pass through the beam splitter prism, the optical power meter reading is M', after the parallel light 6 passes through the beam splitter prism, the optical power meter reading is m', measure the polarized light transmittance of the beam splitter prism At this time, the polarized light transmittance is T 90 =53.40%;

[0071] 3) Take the average of the polarized light transmittance values ​​obtained from the above two measurements to obtain the average transmittance of the beam splitter prism: T=27.56%

[0072] Furthermore, the present embodiment also uses a spectrophotometer to measure the polarized light transmittance of the beam splitting prism again, and the result is 27.85%.

[0073] By comparison, it can be seen that when the present invention is used to test the polarized light transmittance of an optical element, the final measurement error can be controlled within 2%, which has the advantage of high accuracy.

[0074] Furthermore, using a laser as a light source and measuring the transmittance of a beam splitter prism according to a traditional method, the results of multiple measurements are different.

[0075] Parts of the present invention that are not described in detail belong to the common knowledge in the art.

[0076] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A device for measuring polarized light transmittance using a two-position method, characterized in that include: A laser light source (1) is mounted on the collimator (2) and is used to emit linearly polarized laser light toward the collimator (2); A collimator (2) is installed in front of the optical element to be measured, and is used to convert linearly polarized laser light into parallel light (6), to emit the parallel light (6), and to control the laser light source (1) to rotate synchronously and emit the parallel light (6) at different rotation angles; An aperture (3) is installed at the exit of the collimator (2) and is used to adjust the spot size of the exiting parallel light (6); A power measuring device (4) is used to measure the optical power of the parallel light (6) before passing through the optical element to be measured and the optical power of the parallel light (6) after passing through the optical element to be measured at different angles; The processor (5) is used to calculate the average transmittance of the optical element to be measured according to the optical power measured by the power measuring device (4).

2. The device for measuring polarized light transmittance using a two-position method according to claim 1, characterized in that: The laser light source (1) is fixed on the incident focal plane of the collimator (2) and is close to the emission port.

3. The device for measuring polarized light transmittance using a two-position method according to claim 1, characterized in that: The divergence angle of the parallel light (6) emitted by the collimator (2) is less than 1 mrad.

4. The device for measuring polarized light transmittance using a two-position method according to claim 1, characterized in that: The power measuring device (4) comprises a photoelectric detector and an optical power meter, and the optical power meter is connected to the photoelectric detector and the processor (5) respectively.

5. The device for measuring polarized light transmittance using a two-position method according to claim 1, characterized in that: The light spot area of ​​the emitted light is smaller than the detection target surface area of ​​the power measuring device (4).

6. The device for measuring polarized light transmittance using a two-position method according to claim 1, characterized in that: A scale plate for measuring the rotation angle of the collimator (2) is installed at the emission port of the collimator (2).

7. The device for measuring polarized light transmittance using a two-position method according to claim 1, characterized in that: The output power of the laser light source (1) is at the mW level.

8. The device for measuring polarized light transmittance using a two-position method according to claim 1, characterized in that: The collimator (2) is an off-axis reflective collimator.

9. A method for measuring polarized light transmittance using a two-position method, characterized in that The following steps are involved: Step S1: Control the laser light source (1) and the collimator (2) to remain fixed at an initial angle A, first place the power meter (4) in front of the optical element to be measured, measure the optical power of the parallel light (6) before it passes through the optical element to be measured, and record it as M; then place the power meter (4) behind the optical element to be measured, measure the optical power of the parallel light (6) after it passes through the optical element to be measured, and record it as m; The polarized light transmittance T of the optical element to be measured at the initial angle A is obtained based on the optical power M and the optical power m. A ; Step S2: Control the laser light source (1) and the collimator (2) to rotate 90 degrees along the optical axis, repeat step S1, obtain the optical power M' of the collimator (6) before passing through the optical element to be measured and the optical power m' of the collimator (6) after passing through the optical element to be measured, and then obtain the polarized light transmittance T of the optical element to be measured after rotating 90 degrees according to the optical power M' and the optical power m'. A+90 ; Step S3: The processor (5) processes the polarized light transmittance T in step S1. A and the polarized light transmittance T in step S2 A+90 The average transmittance T of the optical element to be tested is calculated.

10. The method for measuring polarized light transmittance using a two-position method according to claim 9, characterized in that: In step S1, the polarized light transmittance T A The calculation formula is: In step S2, the polarized light transmittance T A+90 The calculation formula is: In step S3, the calculation formula of the average transmittance T is:

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